To facilitate the cutting of a keyway in an annular surface of a bore in a workpiece, such as a wheel hub, a pulley hub, collar or sleeve, a broaching bushing is used to support and guide a broach through the workpiece bore. Standard broaching bushings used in most machine shops are round bushings that fit only one size bore. To do all standard size bores, a shop may have to have a large inventory of broaching bushings of different sizes. In addition to the standard size broaching bushings, more bushings may be needed to accommodate bores that are slightly undersize or oversize.
As noted in U.S. Pat. No. 2,510,835 issued Jun. 6, 1950 to A.E. Rice for a Broaching Tool, "In actual practice, a set of broaching elements and guide elements are provided, whereby the operator has a large selection of tools for accommodating workpieces of various sizes and various dimensioned keyway slots."
U.S. Pat. No. 870,971 issued Nov. 12, 1907 to C. Lindstrom for A Device for Cutting Key Seats or the Like was an early disclosure of the use of a elongated guide block of uniform cylindrical dimension throughout its length in form sized to fit into the circular bore in which a keyway was to be cut. The patent suggests that various means, such as a wedge, could be used to firmly lock the guide block in place. The use of the wedge is said to permit the guide block to be used in bores of different diameters. The cylindrical guide block being of uniform dimension, is therefore of uniform circular cross section throughout its length. The placement of the guide block cylindrical surface against an annular interior surface of the workpiece bore, especially when the diameter of the bore is substantially larger than the diameter of the guide block, presents difficulty in aligning the broaching bushing with the axis of the bore and in centering the broaching bushing in the bore.
Accordingly, it is an object of the present invention to provide a broaching bushing assembly the width of which is adjustable to fit a wide range of workpiece bore sizes including bores in which standard size cannot be used because the bore is undersized or oversized.
It is a further object to provide a broaching bushing assembly that includes a wedge shaped member and a broach guide member coacting to form an adjustable broaching bushing assembly having four corner edges which, when placed in contact with diametrically opposite sides of the annular surface of the workpiece bore, align the broach bushing assembly parallel to the axis of the bore and centered in the bore.
It is a further object of the present invention of the present invention to provide a broach bushing assembly in which the broach guide member and the wedge member are longitudinally adjustable relative to one another to size the bushing assembly lateral cross section to fit tightly in the workpiece bore.
It is yet a further object of the present invention to provide a broach bushing assembly in which the abutting sides of the guide member and the wedge member have a longitudinally engageable slot and follower interengagement to prevent lateral displacement of the guide member and wedge member during insertion in the bore and during longitudinal adjustment movements.
It is a further object to provide a broach bushing assembly in which the wedge member has a friction strip on its side engageable with the annular surface of the workpiece to hold the wedge member in place in the bore after preliminary sizing of the assembly in the bore and during final adjustment of the position of the guide member to tightly fit the assembly in the bore.
These and other objects of the present invention will be apparent from the following disclosure of a preferred embodiment of the present invention.